A lithographic apparatus is a machine that applies a desired pattern onto a target portion of a substrate. Lithographic apparatus can be used, for example, in the manufacture of integrated circuits (ICs). In that circumstance, a patterning device, which is alternatively referred to as a mask or a reticle, may be used to generate a circuit pattern corresponding to an individual layer of the IC, and this pattern can be imaged onto a target portion (e.g. comprising part of, one or several dies) on a substrate (e.g. a silicon wafer) that has a layer of radiation-sensitive material (resist). In general, a single substrate will contain a network of adjacent target portions that are successively exposed. Known lithographic apparatus include so-called steppers, in which each target portion is irradiated by exposing an entire pattern onto the target portion in one go, and so-called scanners, in which each target portion is irradiated by scanning the pattern through the beam in a given direction (the “scanning”-direction) while synchronously scanning the substrate parallel or anti-parallel to this direction.
A layer of resist (or other material) is often provided on the surface of a substrate using a spin-coating process. The material used to form the layer is dropped onto the center of the substrate, and the substrate is then rotated. The material flows out towards the edge of the substrate and provides a layer of generally uniform thickness across the surface of the substrate. During the spin-coating process, a thick bead of material is known to form around the edge of the substrate. This bead around the edge of the substrate is commonly referred to as an edge bead. It is desirable to remove this edge bead for a number of reasons. Firstly, it may be difficult or impossible to apply a uniform pattern to, for example, resist forming the edge bead since it is of a greater thickness than resist towards the center of the substrate. Furthermore or alternatively, material forming the edge bead may break off and contaminate the substrate or parts of the lithographic apparatus.